I am not old enough to have used this method of fixing tyres to rims but am old enough to remember seeing others use it.First of all it was only used on track wheels as shellac dries hard and has no residual sticky-ness.This makes it pretty hard to apply a spare out on the road and believe that it will stay on as you round the next bend.Most track riders had a spare pair of wheels with them track side so a change of wheel got them going for the next race.The stuff used was available from french polishing suppliers or hardware shops and came in the form of flakes.I have always been led to believe that it was made from beetles of some sort.The flakes were mixed up with methylated spirits until they dissolved and the mixture applied to both the tyre and the rim.If the rim was brand new it needed to be roughed up a little to encourage adhesion.The rim was coated once and left to dry,often overnight.Then both the rim and the tyre were coated and the tyre applied to the rim.The tyre was then pumped up hard and set aside for 24 hours to set.Shellac being what it is this was a messy process and the stuff dries really hard on both rim and tyre so any excess on the rim needed to be cleaned carefully with metho before this happened.Of course the fact that the rims never saw brake blocks meant that this was about looks as much as anything.Hope this helps, Geoff Duke in Melbourne Australia